Help for Broker Queries
This documentation will contain more information later on
Broker handles many types of queries. The simplest query is
a single keyword, such as:
Searching for common words (like "computer" or "html") may take a lot of
time. Please be considerate of other users.
Particularly for large Brokers, it is often helpful to use more powerful
queries. Harvest supports many different index/search engines, with
varying capabilities. At present, our most powerful (and commonly used)
search engine is Glimpse,
The different types of queries (and how to use them) are discussed below.
Note that you use the same syntax regardless of what index/search engine is
running in a particular Broker, but that not all engines support all of the
above features. In particular, some of the Brokers use WAIS, which
sometimes searches faster than Glimpse but supports only Boolean keyword
queries and the ability to specify result set limits.
- case-insensitive and case-sensitive queries;
- the ability to match parts of words, whole words, or multiple word
phrases (like "resource discovery");
- Boolean (AND/OR) combinations of keywords;
- approximate matches (e.g., allowing spelling errors);
- structured queries (which allow you to constrain matches to certain
- the ability to show matched lines or entire matching records (e.g.,
- the ability to specify limits on the number of matches returned; and
- a limited form of regular expressions (e.g., allowing "wild card"
expressions that match all words ending in a particular suffix).
The different options -
the ability to show matched lines vs. entire matching records,
and the ability to specify match count limits -
can all be specified with buttons and menus in the Broker query forms.
A structured query has the form:
tag-name : value
where tag-name is a Content Summary attribute name, and value
is the search value within the attribute. If you click on a Content
Summary, you will see what attributes are available for a particular
Keyword searches and structured queries can be combined using Boolean
operators (AND and OR) to form complex queries. Lacking parentheses,
logical operation precedence is based left to right.
For multiple word phrases or regular expressions, you need to enclose the
string in double quotes, e.g.,
"internet resource discovery"
Simple keyword search query:
This query will return all objects in the Broker containing
the word Arizona.
Arizona AND desert
This query will return all objects in the Broker that contain both words
anywhere in the object in any order.
This query will return all objects in the Broker that contain
Arizona desert as a phrase. Notice that you need to put
double quotes around the phrase.
Boolean queries with phrases:
"Arizona desert" AND windsurfing
Simple Structured query:
Title : windsurfing
This query will return all objects in the Broker where the Title
attribute contains the value windsurfing.
"Arizona desert" AND (Title : windsurfing)
This query will return all objects in the Broker that contain the phrase
Arizona desert and where
the Title attribute of the same object
contains the value windsurfing.
Query options selected by menus or buttons
These checkboxes allow some control of the query specification.
- Case insensitive:
By selecting this checkbox the query will become case insensitive (lower
case and upper case letters differ). Otherwise, the query will be case
senstive. The default is case insensitive.
- Keywords match on word boundaries:
By selecting this checkbox, keywords will match on word boundaries.
Otherwise, a keyword will match part of a word (or phrase). For example,
"network" will matching "networking", "sensitive" will match "insensitive",
and "Arizona desert" will match "Arizona desertness". The default is to
match keywords on word boundaries.
- Number of errors allowed:
Glimpse allows the search to contain a number of errors. An error is
either a deletion, insertion, or substitution of a single character.
The Best Match option will find the match(es) with the least number of
errors. The default is 0 (zero) errors.
Note: The previous three options do not apply to attribute names.
Attribute names are always case insensitive and allow no errors.
Result set presentation
These checkboxes allow some control of presentation of the query return.
- Display matched lines (from content summaries):
By selecting this checkbox, the result set presentation will contain the
lines of the Content Summary that matched the query. Otherwise, the
matched lines will not be displayed. The default is to display the matched
- Display object descriptions (if available):
Some objects have short, one-line descriptions associated with them. By
selecting this checkbox, the descriptions will be presented. Otherwise,
the object descriptions will not be displayed. The default is to display
- Verbose display:
This checkbox allows you to set whether results are displayed listing
the filename, host, path, and Content Summary each on separate lines, or
just with two lines listing the filename (without a label) and the
Content Summary (with a label). The default is verbose.
Some types of regular expressions are supported by Glimpse.
A regular expression search can be much slower that other searches.
The following is a partial list of possible patterns.
(For more details see the
Glimpse manual pages.)
Regular expressions are currently limited to approximately 30 characters,
not including meta characters. Regular expressions will generally not
cross word boundaries (because only words are stored in the index). So,
for example, "lin.*ing" will find "linking" or "flinching," but not "linear
- ^joe will match "joe" at the beginning of a line.
- joe$ will match "joe" at the end of a line.
- [a-ho-z] matches any character between a and h or
between o and z.
- . matches any single character except newline.
- c* matches zero or more occurrences of the character "c"
- .* matches any number of wild cards
- \* matches the character "*" (\ escapes any of the above